yes aluminum drums, someone must have put a 3.42 posi in it, could this be the same set up as a gn rear, by the way could you lead me to the thread where you got your codes from, thanks
In all probability they added the posi and reused the original gears. One of my posi units came from an '80 Trans-Am. I think it had a 3.08 gear which made the carrier compatible with our 3.42 gear.
While I used to have all these codes memorized, I had to refer to my tattered copy of Steven L. Dove's Buick Grand National, T-Type and GNX The Facts and Figures Book.